The semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area.
As transistor sizes decrease, the size of each feature decreases. One such feature is the shallow trench isolation (STI) used between active areas to isolate one semiconductor device from another and another is the inter-layer dielectric (ILD) between gate structures. Feature size reduction often results in increased aspect ratios because the widths of the openings are smaller but the depths are often the same as before. Techniques used to fill openings (e.g. STIs in substrates or ILDs between gate structures) having lower aspect ratios may provide poor filling results for openings of advanced technologies having high aspect ratios, such as aspect ratios of 8:1 or more.
One alternative to improve filling pertains to using flowable dielectric materials. Flowable dielectric materials, as their name suggest, can flow to fill voids in a gap. Usually, various chemistries are added to the silicon-containing precursors to allow the deposited film to flow. After the flowable film is deposited, it is cured and then annealed to remove the added chemistry to form dielectric layer, e.g., silicon oxide. The flowable film is usually cured and annealed at a high temperature, e.g., greater than 1000° C. to obtain desired mechanical property. In some manufacturing processes, lower temperatures (e.g., between 300° C. and 700° C.) are used to cure and anneal the flowable film due to, e.g., design constraints. When cured at such lower temperatures, mechanical properties, such as the wet etch rate (WER), of the flowable film degrades (e.g., having increased WER), and dishing might occur when the flowable film is recessed by a subsequent process such as a wet etch process.